The invention relates to a fastening means for adapters, in particular cable entries, in wall openings of housings of a wide variety of items of equipment.
Housings of many of such items of equipment are provided in their housing walls with openings or else lead-through eyes which are formed onto and into the housing walls and serve for leading through lines of a wide variety of types, for example electrical supply lines, signal lines or else pressure-medium lines etc., and for bringing these lines up to and connecting them to items of equipment accommodated in such housings. For the sake of simplicity, the openings or lead-through eyes mentioned are referred to in the following generically as xe2x80x9cbushingsxe2x80x9d.
The lines may themselves be conduits or be led up to the housings in conduits or sheaths, for example cable sheaths, and be fastened to the housings in cable entries, threaded adapters of a general type, or else stoppers, referred to in the following as xe2x80x9cadaptersxe2x80x9d. The adapters themselves are screwed, welded and/or adhesively bonded into the bushings. The housings can consequently be used independently of different thread standards of the conduit, sheath or cable connections and, if required, permit the transition from one type of thread, for example an armored thread or metric thread, to another type of thread, for example an imperial thread.
To allow the items of equipment to be manufactured as inexpensively as possible, the housings are today produced from a suitable plastic, for example by the injection-molding process. The adapters, on the other hand, are often manufactured from metal, since they are intended to establish the connection with the usually metallic conduit and sheath connections. On account of the different materials, correspondingly high mechanical stressing of the adapters can lead to deformation of the thin housing wall, consisting of plastic, and to failure of the connection between adapter and housing. A similarly undesired effect may also occur if cable or conduit connections are screwed into threaded adapters screwed in advance into the bushings of the housing and tightened with the aid of a tool. If the plastic at the connecting point is overstressed, the threaded adapter tears out, with the result that particularly thin-walled housings of plastic often do not meet prescribed test or certification criteria.
For example, the US test authority xe2x80x9cFMxe2x80x9d (Factury Mutual) requires of equipment in which only one line is led through a single bushing with a common xc2xexe2x80x3 adapter connection, or smaller, that, in a so-called xe2x80x9ctorque testxe2x80x9d, the housing is not damaged and that the threaded adapter must not be torn out at a tightening or breakaway torque of 90 Nm. For equipment with an adapter connection of up to 1.5xe2x80x3, resistance to as much as 113 Nm is required. The relevant US authority FM also requires for the equipment mentioned that, in a so-called xe2x80x9cbending testxe2x80x9d, adapter connections with a connection of up to xc2xexe2x80x3 with respect to the housing withstand a bending torque of 34 Nm unimpaired; for metallic adapters with a connection from 1xe2x80x3, resistance to as much as 68 Nm is required.
These loads can currently only sometimes be met in the case of plastic housings, by the adapters being adhesively bonded very accurately in the bushings of the housing. Adhesive bonds of this type are, however, complex and consequently expensive. Tests have shown, however, that adhesive bonds of this type fail under loads on the adapters at torques of 90 Nm, as mentioned above.
It is an object of the invention to provide a fastening means with which adapters, in particular threaded adapters, for lines of all types are fastened to the provided bushings of a housing in such a way that the connection does not fail under high loads, in particular complies with the loading tests prescribed by test authorities, even in the case of thin-walled plastic housings, wherever possible without the need for the adapters to be additionally adhesively bonded in the bushings.
This object is achieved according to the invention by a fastening means for adapters and bushings on housings, in particular housings with a wall of small thickness, in which at least two bushings (2a, 2b) are provided, which permit accesses into the housing interior and with, on or in which lines, such as for example signal lines, supply lines or conduits or the like for an item of equipment located in the housing, are fastened by adapters; the fastening means comprising a base plate with at least two openings, which correspond in shape and arrangement to the adapters and the inner surfaces of which are shaped in such a way that the base plate fits positively onto the adapters and the latter are positively braced with respect to one another.
According to another variant of the invention, this object is achieved by fastening means for adapters and bushings on housings, in particular housings with a wall of small thickness, in which at least one bushing is provided, which permits access into the housing interior and with, on or in which a line, such as for example a signal line, a supply line or a conduit or the like for an item of equipment located in the housing, is fastened by means of at least one adapter; the fastening means comprising a base plate with at least one opening, which corresponds in shape and arrangement to the adapter and the inner surface of which is shaped in such a way that the base plate fits positively onto the adapter and the latter is positively braced with respect to the housing by means of at least one securing or bracing element.
In a preferred embodiment of the invention, it is provided that, in the case of housings with adapters which are screwed into the bushing or bushings and respectively have a polygonal external shape, preferably a hexagonal external shape, the respective inner surface of the openings in the base plate of the fastening means is designed as a triangular, hexagonal or dodecagonal shape fitting positively onto the adapters.
According to other preferred embodiments of the invention with more than two openings, the said openings lie in a row on a common line and/or, in the case of an angled plate as the base plate with more than two openings, the openings lie on at least two lines running at an angle, preferably a right angle, with respect to one another.
According to a further embodiment of the invention, the base plate or angled plate has for adaptation to the contour of a housing wall at least one angled-away portion, so that the openings lie in at least two different planes.
According to another embodiment of the invention, the base plate has the shape of an equilateral triangle with rounded-off corners, an opening lying in each corner.
Other embodiments again of the invention relate to a base plate which consists of a glass-fiber-reinforced plastic or of a metal sheet, preferably of stainless steel.
In a further embodiment of the fastening means according to the invention, the securing or bracing element is a specially shaped recess of the base plate into which a corresponding projection of the housing acts in an engaging or positive manner.
According to another embodiment, the securing or bracing element comprises at least one cranked projection which is formed onto the base plate and interacts with a corresponding abutment of the housing.
The invention is based on the idea that, when fitting the fastening means according to the invention onto the adapters fastened in the bushings, in particular screwed in there and aligned by turning, they are connected to one another in such a way that, when screwing in and tightening cable connections or other lines into the adapters, overstressing of the adapter connections, in particular threaded connections, is avoided and consequently possible breaking out of the adapters is avoided. The torque acting during tightening of the line connections is converted into a more favorable bending load.
A further particular advantage of a fastening means according to the invention produced from a metal sheet is that differences in potential occurring at the connections are equalized, which leads to greater safety for the equipment.
In addition, fastening means can be manufactured from a metal sheet or from plastic in a simple and low-cost way, for example by laser cutting.